Data Lineage in relation to Cognos is how an item on your report can be traced back to the source.
If you want to know where a dataitem comes from follow the next steps:
1. In your report, expand the “insertable objects” three
2. Right click for example on a measure
3. Choose “Lineage”
4. A new screen pops up where you will see the Data Lineage information being gathered
5. In the next screen you will have a tab for “Business View” and “Technical View”